1. Field of the Invention
The present invention relates to a projection display apparatus which includes; a light source, a light valve configured to modulate light emitted from the light source, and a projection unit configured to project light emitted from the light valve on a projection plane.
2. Description of the Related Art
Recently, there has been known a projection display apparatus including a solid light source such as a laser light source, a light valve configured to modulate light emitted from the solid light source, and a projection unit configured to project the light outputted from the light valve on a projection plane.
Here, a long distance between the projection unit and the projection plane needs to be assured for displaying a large-size image on the projection plane. To address this, a projection display system has been proposed which aims to shorten the distance between the projection unit and the projection plane by using a reflection mirror configured to reflect the light, outputted from the projection unit, toward the projection plane (for example, Japanese Patent Application Publication No. 2006-235516 and Japanese Patent Application Publication No. 2008-250280).
Meanwhile, wall projection and floor projection are possible by changing the way the housing case of the projection display apparatus is placed. Specifically, when the housing case is placed according to wall-projection placement, the projection display apparatus projects light emitted from a light valve on a projection plane provided on a wall surface. On the other hand, when the housing case is placed according to floor-projection placement, the projection display apparatus projects light emitted from the light valve on a projection plane provided on a floor surface.
The housing case generally has a substantially rectangular parallelepiped shape. Accordingly, with the projection display apparatus having a housing case whose placement is changeable, it is difficult to determine whether the housing case is placed correctly or not.